Lightning and Engines: NOx
How nitrogen oxides form in air
What this lesson covers
Why it matters
The atmosphere is mostly nitrogen, yet it refuses to react with oxygen under normal conditions. Lightning provides the violent energy needed to force this union.
The idea in plain words
Preview: the NO you just made won't stay colourless for long — it meets more oxygen on the way down.
Predict first
Why do N₂ and O₂ only combine during lightning or in hot engines?
Nitrogen gas has a strong triple bond. Only extreme heat from lightning or combustion provides enough energy to break it and allow combination with oxygen.
- Nitrogen is too heavy to react
- The triple bond in N₂ requires high energy to break — correct
- Oxygen repels nitrogen at room temperature
- They need a catalyst like iron to react
What you do
Balance N₂ + O₂ → NO: how many NO molecules must form from one N₂ and one O₂ so no atom is lost? The scale only settles when you get it right.
Check yourself
What is the chemical equation for the formation of nitrogen monoxide?
The reaction produces nitrogen monoxide (NO), not dioxide. The balanced equation is N₂ + O₂ → 2NO.
Which condition is essential for this reaction to occur?
The strong triple bond in nitrogen requires very high temperatures, such as those found in lightning strikes or internal combustion engines, to break.
- N₂ + O₂ → NO₂
- N₂ + O₂ → 2NO — correct
- 2N + 2O → 2NO
- Presence of a catalyst
- Very high temperature — correct
- Electrolysis
- Low pressure